In 1949, the Air Force conducted initial testing with a little known experiment to evaluate wing tip coupling with a Douglas C-47 Skytrain and a Culver Q-14 Cadet at the Wright Air Development Center at Wright Field in Ohio. Theory predicted that increasing the aspect ratio of an airplane wing by attaching another wing at its tip improved aerodynamic efficiency, offsetting the drag of the smaller plane. A bomber would be able to tow a fighter into a combat zone with little loss of range.

As expected, this idea proved to be highly dangerous, and even more so once experimentation began with larger and faster aircraft.

The biggest problem was the extreme vortex that was generated at the wingtips of the EB-29A, which caused the attached parasites to roll violently. The entire three-plane EF-84B/EB-29A/EF-84B array crashed as a unit on April 24, 1953, killing all the crewmembers. The project was terminated shortly thereafter.

Yeah it was so early in the project that they hadn't put much thought into it. Even at that it was cancelled due to the danger level before it could even be improved upon. With the introduction of airtankers this idea was simply impractical much like the parasite fighters also in development at the time.

I was so surprised to read this that I had to read more, here is somthing from Wikipedia, I know their info is is not always correct but I think you will find this interesting.

EF-84DTwo F-84Ds, EF-84D 48-641 and EF-84D 48-661 were modified with coupling devices; 641 starboard wing, 661 port wing for "Tip-Tow Project MX106 Wing Coupling Experiments." An EB-29A 44-62093 was modified with coupling devices on both wings. Because of the difference in landing gear lengths, the three aircraft took off separately and couple/uncoupled in-flight. The pilot of 641 was Major John M. Davis and the pilot of 661 was Major C.E. "Bud" Anderson."One of the more interesting experiments undertaken to extend the range of the early jets in order to give fighter protection to the piston-engine bombers, was the provision for in-flight attachment/detachment of fighter to bomber via wingtip connections. One of the several programs during these experiments was done with a B-29 mother ship and two F-84D 'children', and was code named 'Tip Tow'. A number of flights were undertaken, with several successful cycles of attachment and detachment, using, first one, and then two F-84s. The pilots of the F-84s maintained manual control when attached, with roll axis maintained by elevator movement rather than aileron movement. Engines on the F-84s were shut down in order to save fuel during the 'tow' by the mother ship, and in-flight engine restarts were successfully accomplished. The experiment ended in disaster during the first attempt to provide automatic flight control of the F-84s, when the electronics apparently malfunctioned. The left hand F-84 rolled onto the wing of the B-29, and the connected aircraft both crashed with loss of all on board personnel (Anderson had uncoupled so was did not crash with the other two aircraft)."[8]F-84E